Herpes simplex virus (HSV) is a ubiquitous human pathogen capable of causing a variety of clinically important diseases. The role of the immune response in controlling primary and recurrent HSV infection is under investigation. HSV glycoprotein C (gC) is highly immunogenic for both humoral and cellular immune responses and consequently plays a major role in the immunobiology of infection. The central aims of this competing renewal application are (i) to develop a more complete understanding at the molecular level of the antigenic structure of gC as recognized by both antibodies and cytotoxic T lymphocytes (CTL), with an emphasis on a comparative analysis of the organization of antigenic domains and component epitopes between gC of the two serotypes and (ii) to explore the potential usefulness of gC as a subunit vaccine against virus-induced encephalitis and zosteriform lesions using the mouse as a model host. The central hypothesis to be tested is that the antigenic domains of gC-1 and gC-2 are colinear and that the predominant type-specificity exhibited by these domains is due to the presence of dissimilar amino acids within the component epitopes. The experimental strategy for defining type-specific epitope structure and organization will be to compare the reactivity of large panels of gC-1 and gC-2 specific mAbs with (i) a series of genetically engineered gC-1:gC-2 chimeric gene products and (ii) panels of wild-type and mutant synthetic peptides. The peptides will also be used to develop antibody reagents to discover new antigenic determinants and for a more detailed analysis of known antigenic sites. Correlation of the epitope mapping studies with antigenic variation among fresh clinical isolates will be sought in order to assess the stability of epitope structure and to detect genetically invariant domains. Studies of the CTL responses to HSV gC will be continued using short-term and long-term CTL clones to (i) confirm that gC of both serotypes is the major inducer and target antigen for CTLs (ii), define CTL-specific epitopes at a molecular level, and (iii) determine the extent to which the B and T cell repertoires overlap in their recognition of gC. Finally, purified gC derived with a baculovirus expression vector system in combination with synthetic peptides will be used in immunization protocols to induce protective immunity against HSV-induced neurological and peripheral lesions with emphasis on prevention of latent infection of ganglion neurons.